// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_EMULATE_ARRAY_H
#define EIGEN_EMULATE_ARRAY_H

// The array class is only available starting with cxx11. Emulate our own here
// if needed. Beware, msvc still doesn't advertise itself as a c++11 compiler!
// Moreover, CUDA doesn't support the STL containers, so we use our own instead.
#if (__cplusplus <= 199711L && EIGEN_COMP_MSVC < 1900) || defined(EIGEN_GPUCC) || defined(EIGEN_AVOID_STL_ARRAY)

namespace Eigen {
template <typename T, size_t n> class array
{
public:
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& operator[](size_t index)
    {
        eigen_internal_assert(index < size());
        return values[index];
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& operator[](size_t index) const
    {
        eigen_internal_assert(index < size());
        return values[index];
    }

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& at(size_t index)
    {
        eigen_assert(index < size());
        return values[index];
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& at(size_t index) const
    {
        eigen_assert(index < size());
        return values[index];
    }

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& front() { return values[0]; }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& front() const { return values[0]; }

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& back() { return values[n - 1]; }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& back() const { return values[n - 1]; }

    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE static std::size_t size() { return n; }

    T values[n];

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array() {}
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v)
    {
        EIGEN_STATIC_ASSERT(n == 1, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2)
    {
        EIGEN_STATIC_ASSERT(n == 2, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3)
    {
        EIGEN_STATIC_ASSERT(n == 3, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4)
    {
        EIGEN_STATIC_ASSERT(n == 4, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
        values[3] = v4;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5)
    {
        EIGEN_STATIC_ASSERT(n == 5, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
        values[3] = v4;
        values[4] = v5;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6)
    {
        EIGEN_STATIC_ASSERT(n == 6, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
        values[3] = v4;
        values[4] = v5;
        values[5] = v6;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6, const T& v7)
    {
        EIGEN_STATIC_ASSERT(n == 7, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
        values[3] = v4;
        values[4] = v5;
        values[5] = v6;
        values[6] = v7;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6, const T& v7, const T& v8)
    {
        EIGEN_STATIC_ASSERT(n == 8, YOU_MADE_A_PROGRAMMING_MISTAKE)
        values[0] = v1;
        values[1] = v2;
        values[2] = v3;
        values[3] = v4;
        values[4] = v5;
        values[5] = v6;
        values[6] = v7;
        values[7] = v8;
    }

#if EIGEN_HAS_VARIADIC_TEMPLATES
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array(std::initializer_list<T> l)
    {
        eigen_assert(l.size() == n);
        internal::smart_copy(l.begin(), l.end(), values);
    }
#endif
};

// Specialize array for zero size
template <typename T> class array<T, 0>
{
public:
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& operator[](size_t)
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& operator[](size_t) const
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& front()
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& front() const
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE T& back()
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }
    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE const T& back() const
    {
        eigen_assert(false && "Can't index a zero size array");
        return dummy;
    }

    static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE std::size_t size() { return 0; }

    EIGEN_DEVICE_FUNC
    EIGEN_STRONG_INLINE array() : dummy() {}

#if EIGEN_HAS_VARIADIC_TEMPLATES
    EIGEN_DEVICE_FUNC array(std::initializer_list<T> l) : dummy()
    {
        EIGEN_UNUSED_VARIABLE(l);
        eigen_assert(l.size() == 0);
    }
#endif

private:
    T dummy;
};

// Comparison operator
// Todo: implement !=, <, <=, >,  and >=
template <class T, std::size_t N> EIGEN_DEVICE_FUNC bool operator==(const array<T, N>& lhs, const array<T, N>& rhs)
{
    for (std::size_t i = 0; i < N; ++i)
    {
        if (lhs[i] != rhs[i])
        {
            return false;
        }
    }
    return true;
}

namespace internal {
    template <std::size_t I_, class T, std::size_t N> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& array_get(array<T, N>& a) { return a[I_]; }
    template <std::size_t I_, class T, std::size_t N> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& array_get(const array<T, N>& a) { return a[I_]; }

    template <class T, std::size_t N> struct array_size<array<T, N>>
    {
        enum
        {
            value = N
        };
    };
    template <class T, std::size_t N> struct array_size<array<T, N>&>
    {
        enum
        {
            value = N
        };
    };
    template <class T, std::size_t N> struct array_size<const array<T, N>>
    {
        enum
        {
            value = N
        };
    };
    template <class T, std::size_t N> struct array_size<const array<T, N>&>
    {
        enum
        {
            value = N
        };
    };

}  // end namespace internal
}  // end namespace Eigen

#else

// The compiler supports c++11, and we're not targeting cuda: use std::array as Eigen::array
#include <array>
namespace Eigen {

template <typename T, std::size_t N> using array = std::array<T, N>;

namespace internal {
/* std::get is only constexpr in C++14, not yet in C++11
 *     - libstdc++ from version 4.7 onwards has it nevertheless,
 *                                          so use that
 *     - libstdc++ older versions: use _M_instance directly
 *     - libc++ all versions so far: use __elems_ directly
 *     - all other libs: use std::get to be portable, but
 *                       this may not be constexpr
 */
#if defined(__GLIBCXX__) && __GLIBCXX__ < 20120322
#define STD_GET_ARR_HACK a._M_instance[I_]
#elif defined(_LIBCPP_VERSION)
#define STD_GET_ARR_HACK a.__elems_[I_]
#else
#define STD_GET_ARR_HACK std::template get<I_, T, N>(a)
#endif

    template <std::size_t I_, class T, std::size_t N> constexpr inline T& array_get(std::array<T, N>& a) { return (T&)STD_GET_ARR_HACK; }
    template <std::size_t I_, class T, std::size_t N> constexpr inline T&& array_get(std::array<T, N>&& a) { return (T &&) STD_GET_ARR_HACK; }
    template <std::size_t I_, class T, std::size_t N> constexpr inline T const& array_get(std::array<T, N> const& a) { return (T const&)STD_GET_ARR_HACK; }

#undef STD_GET_ARR_HACK

}  // end namespace internal
}  // end namespace Eigen

#endif

#endif  // EIGEN_EMULATE_ARRAY_H
